The present invention relates to automatic transmissions in which the torque converter is locked by a clutch mechanism to prevent slippage at certain times, and particularly to an apparatus and method for attachment of replacement frictional lining material to a lock-up piston face.
In order to obtain better efficiency, some automatic transmissions for automobiles include a clutch mechanism which, when engaged, locks the turbine portions of the torque converter to each other to prevent relative movement, and thus transmits power directly from the engine to the gearbox without slippage of the torque converter. In such transmissions the clutch includes a "lock-up" piston having a lining of frictional material which is held in contact with another portion of the torque converter to lock up the torque converter. Ordinarily the torque converter is "locked up" only when the vehicle is operating at highway speeds.
As part of the course of rebuilding an automatic transmission including the torque converter lock-up capability, it is necessary to replace the worn lining of frictional material, which is bonded adhesively to the lock-up piston. The lock-up piston must be prepared by removal of all traces of the original friction lining and adhesive materials, and a new annular lining ring of frictional material, furnished pre-coated with an adhesive, must then be fastened to the lock-up piston. The process of installing the new lining requires attachment to the lock-up piston through the application of high temperature and pressure to activate the adhesive material.
Previously, the required pressure and temperature have been obtained by transmission rebuilding shops only by the use of multiple clamps, heating the lock-up piston after the replacement lining material has been clamped to the piston by placing the clamped piston and friction material in an oven for a relatively long time. Adhesive bonding of frictional linings to lock-up pistons in this manner not only requires longer time than is desired, but utilizes undesirably large amounts of energy to heat the lock-up piston and lining in an oven. In addition, this method requires more labor than is desired, as well as a considerable amount of care, in placement of the lining material on a lock-up piston and in maintaining that position during attachment of clamps prior to heating of the entire assembly.
What is desired, therefore, is an improved apparatus and method for attaching replacement frictional lining material to a lock-up piston for a torque converter of an automatic transmission. Preferably, such apparatus should easily and automatically provide the required temperature and pressure, concentrated where required to attach a frictional lining to a lock-up piston quickly and easily and with safety to the operator.